Thread cutting tools

ABSTRACT

Tools for cutting threads in certain extremely hard materials like the aluminum bronzes, such tool being characterized by four lineal arrays of teeth equally spaced around a longitudinal axis and substantially equidistant therefrom. One pair of said arrays has a series of long teeth interspersed with a series of short teeth, and the other such pair has teeth of uniform length which are slightly shorter than the long teeth in the first mentioned arrays. An inwardly inclined chip clearance surface on each tooth extends rearwardly to a point below the root of the tooth. A flat cutting face on the teeth in each pair of lineal arrays extends below the root thereof, and is disposed at substantially right angles to a transverse medial plane through the other pair of lineal arrays.

-May 9,1972

United States Patent Simonffy [54] THREAD CUTTING TOOLS V LouisSimonffy, 7253 West Lafayette, agfi ABSTRACT [22] Filed: Oct. 12, 1970Tools for cutting threads in certain extremely hard materials like thealuminum bronzes, such tool being characterized by four lineal arrays ofteeth equally spaced around a longitudinal axis and substantiallyequidistant therefrom. One pair of said arrays has a series of longteeth interspersed with a series of short teeth, and the other such pairhas teeth of uniform length which are slightly shorter than the longteeth in the first mentioned arrays. An inwardly inclined chip clearancesurface on each tooth extends rearwardly to a 2 1. ZMNZ 2 52 /0 i l m mm4 m I u m "h 7 1. u Q m In N l m 1 C C P .M P s mk A U IF 1 11 .l 2 1002 5 55 l i [.1

point below the root of the tooth, A flat cutting face on the teeth ineach pair oflineai arrays extends below the root thereof, and isdisposed at substantially right angles to a transverse medial planethrough the other pair of lineal arrays.

S T. N m MA n E MT m MS e m H N U s U 2,024,169 12/1935Koonz..............

1,293,432 2/1919 Higgins..................................408/2193Claims,6DrawingFigures THREAD CUTTING TOOLS BACKGROUND OF THE INVENTIONThis invention relates generally to thread cutting tools, but moreparticularly to taps and dies for use in working extremely hardmaterials, such as the aluminum bronzes. Conventional taps and dies,when used on this material have a tendency to over-heat, bind andeventually break, even though coolants, lubricants, and cuttingcompounds are employed. For this reason, the applicant has designedteeth for taps and dies which enables them readily to cut threads inaluminum bronze.

SUMMARY OF THE INVENTION This invention consists of thread cutting toolseach comprising a body having four laterally spaced lineal arrays ofteeth substantially equidistant from the longitudinal axis of the body.One pair of the lineal arrays has a series of long teeth interspersedwith a series of short teeth. The other pair of lineal arrays has teethof uniform length which are slightly shorter than the long teeth in thefirst mentioned pair. An inwardly inclined chip clearance surface oneach tooth extends rearwardly to a point below the root of the tooth. Aflat cutting face on each tooth extends approximately 0.020 inch belowthe root thereof, with said faces on each pair of lineal arrays beingdisposed at substantially right angles to a transverse medial planethrough the other pair of lineal arrays.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevation view of atap embodying the applicants invention, showing the spaced groups ofshort and fullsize long teeth 30 and 28 respectively on lineal arrays 14and 16.

FIG. 2 is a side elevation view, taken substantially on plane 22 in FIG.1, showing the short teeth 36 of uniform length, on lineal arrays 18 and20.

FIG. 3 is an enlarged section view, taken substantially on plane 3-3 inFIG. 2, showing the cutting faces 46 and the clearances 40 on the teethin the four lineal arrays 14,16,18 and 20.

FIG. 4 is a top plan view of a die embodying the applicant's invention,showing the cutting faces 86 and the clearance surfaces 80 on the teeth.

FIG. 5 is a section view, taken substantially on plane 5--5 in FIG. 4,showing the short teeth 78 of uniform length on lineal arrays 64 and 65.

FIG. 6, is a section view, taken substantially on plane 6-6 in FIG. 4,showing the spaced groups of short and full-size long teeth 72 and 70respectively on lineal arrays 62 and 63.

CONSTRUCTION For a more detailed description of the invention, referenceis made to FIGS. 1,2 and 3 of the drawing, in which numeral 10designates a tap with an elongated fluted body 12 having thereon fourlineal arrays of teeth 14,16,18 and are substantially equidistant fromthe longitudinal axis 22 of the elongated fluted body 12, and angularlyspaced from each other by approximately 90.

A chamfered or tapered section 26 is provided on allthe teeth at theforward end of the elongated fluted body 12. Oppositely disposed linealarrays 14 and 16 have a series of fullsize long teeth 28, and a seriesof teeth 30 which are at least 0.006 inch shorter. The full-size longteeth 28 are arranged in spaced groups of two each, with the mostforwardly disposed group being located immediately adjacent thechamfered section 26.

The series of shorter teeth 30 are arranged in groups of at least twoeach, which are positioned in the spaces between the groups of full-sizelong teeth 28, as shown in FIG. 1. A land 32, on each of the teeth 28and 30 in lineal arrays 14 and 16, has a lateral width, shown by 34 inFIG. 3, which may be varied in size from 0.003 to 0.005 inch for optimumresults.

The other oppositely disposed lineal arrays 18 and 20 have teeth 36 ofuniform length which are at least 0.006 inch shorter than the full-sizelong teeth 28 in the lineal arrays 14 and 16, shown by 38 in FIG. 3. Aninwardly disposed flat chip clearance surface 40 is provided on each ofthe teeth in the four lineal arrays 14, 16,18 and 20, which extendsrearwardly from the trailing edge on each tooth to a point 42 adjacentthe heel thereon which is 0.015 to 0.025 inch below the root 44 of thetooth, shown by 43 in FIG. 3.

A flat cutting face 46 on the forward side of each tooth in the fourlineal arrays 14,16,18 and 20, extends 0.020 inch below the root 44 ofthe tooth, as shown by 48 in FIG. 3, and is substantially parallel tothe longitudinal axis 22 of the elongated fluted body 12. The flatcutting faces 46 on the teeth 28 and 30 in one pair of the lineal arrays14 and 16, are all disposed at an angle 50 of substantially 90 to atransverse medial plane 52 between the other pair of lineal arrays 18and 20.

For optimum results the angle 50 should not be varied by more than 2. Inpractice, when making taps for cutting larger threads, the teeth 36 ofuniform length in lineal arrays 18 and 20, are further shortened, andmade as much as 0.015 inch shorter than the long teeth 28 in linealarrays 14 and 16 to prevent binding and insure optimum results.

body 60, and angularly spaced from each other by approximately 90. Achamfered or tapered section 68 is provided on all the teeth at theforward end of the cylindrical body 60.

Oppositely disposed lineal arrays 62 and 63 have therein a series offull'size long teeth 70, and a series of short teeth 72, which are atleast 0.006 shorter than the full-size long teeth 70. The full-size longteeth 70 are arranged in spaced groups of two each, with the mostforwardly disposed group being located immediately adjacent thechamfered or tapered section 68.

The series of short teeth 72 are arranged in groups of at least twoeach, and positioned in the spaces between the groups of full-size teeth70, as shown in FIG. 6. The land 74 on each of the teeth in the linealarrays 62 and 63, has a lateral width, shown by 76 in FIG. 4, which maybe varied in size from 0.003 to 0.005 inch for optimum results. Theother oppositely disposed lineal arrays 64 and 65 have teeth 78 ofuniform length, which are at least 0.006 inch shorter than the full-sizelong teeth 70 in the lineal arrays 62 and 63, as shown by 79 in FIG. 4.

An inwardly disposed flat chip clearance surface 80 is provided on eachof the teeth in the four lineal arrays 62,63,64 and 65, which extendsrearwardly from the trailing edge of each tooth to a point 82 adjacentthe heel thereon which is 0.015 to 0.025 inch below the root 84 of thetooth, shown by 83 in FIG. 4. A flat cutting face 86 on the forward sideof each tooth in the four lineal arrays 62,63,64 and 65, extends 0.020inch below the root 84 of the tooth, as shown by 88 in FIG. 4, and issubstantially parallel to the longitudinal axis 66 of the cylindricalbody 60.

The flat cutting faces 86 on the teeth in one pair of the lineal arrays62 and 63, are all disposed at an angle 89 of substantially 90 to atransverse medial plane 90 between the other pair of lineal arrays 64and 65. For optimum results the angle 89 should not be varied by morethan 2. In practice, when making dies for cutting larger threads, theteeth 78 of uniform length in lineal arrays 64 and 65, are furthershortened, and made as much as 0.015 inch shorter than the full-sizelong teeth 70 in lineal arrays 62 and 63 to prevent binding and insureoptimum results.

In practice, the size opening specified for a particular tap specifiedfor a particular thread size should be decreased by at least 0.004 inch.The applicant's taps and dies were designed and intended for useespecially with the aluminum bronzes, and are accordingly unsuited foruse in working softer materials such as copper and brass.

Based upon the foregoing discussion, the applicant is of the opinionthat his invention has fulfilled a long-felt need in the field of threadcutting tools, and that hehas accordingly made a valuable contributionto the related art. However, while the invention was described withreference to the structural details of a limited number of embodiments,it will be appreciated by those familiar with the art that theprinciples involved are susceptible of numerous other practicaladaptations.

1 therefore claim as new, and desire to secure by Letters Patent:

1. A thread cutting tool comprising a body, four lineal arrays of teethon the body substantially equidistant from the longitudinal axis thereofand angularly spaced from each other by 90", a chamfered section on theteeth at the forward end of the body, one oppositely disposed pair ofsuch lineal arrays having a series of long teeth interspersed with aseries of short teeth, the other oppositely disposed pair of such linealarrays having teeth of uniform length which are shorter than the longteeth in the first mentioned pair of lineal arrays, a land on each ofthe teeth in the first mentioned pair of lineal arrays having a lateralwidth which may vary from 0.003 to 0.005 inch, an inwardly andrearwardly disposed chip clearance surface on each tooth of the fourlineal arrays extending from the trailing edge of the land thereon to apoint adjacent the heel of such tooth which is at least 0.015 inch belowthe root thereof, and a flat cutting face on each tooth in the fourlineal arrays extending at least 0.020 inch below the root of the tooth,said cutting faces on the teeth of each pair of lineal arrays beingdisposed at substantially right angles to a transverse medial planethrough the other pair of lineal arrays.

2. The thread cutting tool of claim 1 in which the series of long teethon the first mentioned pair of lineal arrays comprises spaced groups oftwo teeth each and the series of short teeth consists of groups havingat least two teeth each, all of which are at least 0.006 inch shorterthan the long teeth, with said groups of shorter teeth being located inthe spaces between the groups of long teeth.

3. The thread cutting tool of claim 2 in which the series of long teethon the first mentioned pair of lineal arrays has the most forwardlydisposed group thereof located immediately adjacent the chamferedsection on the body.

1. A thread cutting tool comprising a body, four lineal arrays of teethon the body substantially equidistant from the longitudinal axis thereofand angularly spaced from each other by 90*, a chamfered section on theteeth at the forward end of the body, one oppositely disposed pair ofsuch lineal arrays having a series of long teeth interspersed with aseries of short teeth, the other oppositely disposed pair of such linealarrays having teeth of uniform length which are shorter than the longteeth in the first mentioned pair of lineal arrays, a land on each ofthe teeth in the first mentioned pair of lineal arrays having a lateralwidth which may vary from 0.003 to 0.005 inch, an inwardly andrearwardly disposed chip clearance surface on each tooth of the fourlineal arrays extending from the trailing edge of the land thereon to apoint adjacent the heel of such tooth which is at least 0.015 inch belowthe root thereof, and a flat cutting face on each tooth in the fourlineal arrays extending at least 0.020 inch below the root of the tooth,said cutting faces on the teeth of each pair of lineal arrays beingdisposed at substantially right angles to a transverse medial planethrough the other pair of lineal arrays.
 2. The thread cutting tool ofclaim 1 in which the series of long teeth on the first mentioned pair oflineal arrays comprises spaced groups of two teeth each and the seriesof short teeth consists of groups having at least two teeth each, all ofwhich are at least 0.006 inch shorter than the long teeth, with saidgroups of shorter teeth being located in the spaces between the groupsof long teeth.
 3. The thread cutting tool of claim 2 in which the seriesof long teeth on the first mentioned pair of lineal arrays has the mostforwardly disposed group thereof located immediately adjacent thechamfered section on the body.